Wireless communications are widely used in various kinds of devices and/or systems for transmitting data. For example, a wireless alignment system provides alignment sensors with wireless transceivers for attaching to or contacting with vehicle wheels or vehicle body to obtain data related to alignment parameters thereof, such as toe angles, camber, caster, vehicle body centerline, wheelbase, etc. The data obtained by the sensors are transmitted by the transceiver associated with each sensor to a host for further processing. Examples of wireless alignment systems are discussed in U.S. Pat. No. 5,592,383, titled “WHEEL ALIGNER CORDLESS COMMUNICATIONS UNIT,” and U.S. Pat. No. 4,761,749, titled “VEHICLE WHEEL ALIGNMENT APPARATUS AND METHOD.” Both of the above-referenced patents are commonly assigned to the assignee of this application, and incorporated herein by reference in their entireties.
However, wireless communications between the host and sensors usually are susceptible to interference by signals sent to and from other hosts and/or sensors of the same type. Conventional wireless systems avoid interferences from other sensors and/or hosts by allocating different channels for each sensor using different frequency bands or hopping sequences. However, available frequency bands are limited. As the number of sensors increase, the number of sensors will exceed available channels.
Furthermore, wireless alignment sensors may be used with different vehicle wheels or parts. In other words, the sensors are swappable. For example, an alignment sensor may be used to measure parameters of the right front wheel of vehicle A in a first alignment service, but may be used to measure parameters of the left right wheel of vehicle B in a second alignment service. Thus, in order for a host to correctly calculate alignment parameters, the host needs to identify which wheel of the vehicle that the received signals are associated to.
In addition, in a vehicle service center, there are usually a plurality of alignment systems servicing numerous vehicles at the same time, which involves a large number of alignment sensors communicating with the same host or different hosts. As all the hosts and/or alignment sensors are located within effective communication distances, signals sent by alignment sensors of one alignment system can be received by a host of another alignment system in the service center, which will cause errors if the host calculates alignment parameters of a vehicle under service using positional parameters from other vehicles. Thus, the host also needs to identify whether a received signal indeed come from an alignment sensor of a specific alignment system.